Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a mediumstrength aged AI-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanc...Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a mediumstrength aged AI-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al-Zn-Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η＇ precip- itates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging. Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al-Zn-Mg alloys are independent of Ag addition.展开更多
The CR superconducting magnet is a dipole of the FAIR project of GSI in Germany.The quench of the strand is simulated using FEM software ANSYS.From the simulation,the quench propagation can be visualized. Programming ...The CR superconducting magnet is a dipole of the FAIR project of GSI in Germany.The quench of the strand is simulated using FEM software ANSYS.From the simulation,the quench propagation can be visualized. Programming with APDL,the value of propagation velocity of normal zone is calculated.Also the voltage increasing over time of the strand is computed and pictured.Furthermore,the Minimum Propagation Zone(MPZ)is studied. At last,the relation between the current and the propagation velocity of normal zone,and the influence of initial temperature on quench propagation are studied.展开更多
基金financially supported by the National Key Research and Development Program of China (No. 2016YFB0300900)the National Natural Science Foundation of China (No. 51171209)
文摘Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a mediumstrength aged AI-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al-Zn-Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η＇ precip- itates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging. Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al-Zn-Mg alloys are independent of Ag addition.
文摘The CR superconducting magnet is a dipole of the FAIR project of GSI in Germany.The quench of the strand is simulated using FEM software ANSYS.From the simulation,the quench propagation can be visualized. Programming with APDL,the value of propagation velocity of normal zone is calculated.Also the voltage increasing over time of the strand is computed and pictured.Furthermore,the Minimum Propagation Zone(MPZ)is studied. At last,the relation between the current and the propagation velocity of normal zone,and the influence of initial temperature on quench propagation are studied.
